A gas turbine engine generally includes a compressor section, a combustion section, and a turbine section. The combustion section typically includes at least one combustor which includes a fuel nozzle and a combustion liner positioned within a combustor casing. The combustion liner defines a primary combustion chamber within the combustor downstream from the fuel nozzle. The combustion liner may be circumferentially surrounded by a sleeve such as an impingement sleeve or a flow sleeve.
The sleeve is radially spaced from the combustion liner and a flow or cooling passage is defined therebetween. In particular configurations, a fuel injector extends radially through the sleeve, the cooling passage and the combustion liner. The fuel injector is axially staged or positioned downstream from the fuel nozzle(s). In particular configurations, a boss extends from the sleeve to the liner. The boss defines and/or circumferentially surrounds an opening in the combustion liner. The fuel injector extends radially within the boss and terminates proximate to the opening in the combustion liner. In order to accommodate the fuel injector, the boss must be sized larger than the fuel injector.
During operation of the combustor, compressed air flows through the cooling passage, past the boss and into a head-end volume of the combustor. The relatively large boss creates a bluff body or flow restriction within the cooling passage which results in non-uniform flow through the cooling passage upstream from the head-end volume. Once the compressed air reaches the head-end volume, it reverses flow direction and enters the fuel nozzle and/or the primary combustion chamber. Non-uniformity of the compressed air flowing into the head-end volume and into the fuel nozzle may effect overall combustor performance.